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Taj Patterson, after suffering an assault by a gang of men in Williamsburg in December 2013.

A defense expert testified that the DNA testing method used to link Mayer Herskovic to a brutal 2013 assault on a gay black man in Williamsburg was invalid and that his DNA may have ended up on the victim’s sneaker because a third person first touched Herskovic and then touched the sneaker.

“There is a question of potential secondary transfer to the sneaker,” said Heather Coyle, an associate professor at the University of New Haven who previously worked in Connecticut’s criminal forensics lab, in Brooklyn Supreme Court on September 19.

Herskovic is charged with multiple counts of unlawful imprisonment, assault, gang assault, and menacing in the early morning December 1, 2013 attack that left Taj Patterson blind in one eye. Patterson was brutally attacked by a mob of men, and two among them, both affiliated with a private Hasidic community patrol, earlier pleaded guilty to unlawful imprisonment.

University of New Haven professor says defendant’s marker could have been left by another party

While no witness has identified Herskovic as the assailant, Patterson testified on August 31 that the man who punched him in the face, jabbed a thumb in his eye, and kicked him in the face is the same man who removed his sneaker and tossed it onto a nearby roof.

Police recovered the sneaker from the roof, and it was checked for fingerprints and DNA. On August 30, a criminalist from the city medical examiner’s office testified that Herskovic’s DNA was found on the sneaker that police recovered from the roof.

The testimony on the DNA testing method, called high sensitivity DNA testing, was technical and focused on the amount of DNA tested and the software used in analyzing the results. The city medical examiner’s office is the only public crime lab in the US that does this type of testing. One Brooklyn court would not allow DNA evidence developed with this method to be used at a trial.

High sensitivity testing uses DNA samples that are measured in picograms, or trillionths of a gram. The medical examiner uses the method to test samples that are less than 100 picograms. DNA test kit manufacturers recommend using DNA samples of at least one nanogram, or 1,000 picograms, Coyle said.

The DNA is amplified, or has copies of it reproduced, and then compared to known DNA samples, in this case those from Herskovic and Patterson. The medical examiner’s office uses its own proprietary software, called the Forensic Statistical Tool, to perform an analysis and offer an opinion on how likely it is that a particular individual contributed DNA to a sample.

Coyle said that the small sample was prone to error being introduced during amplification and when the software performs the analysis on the sample. Pointing to the medical examiner’s evidence, she said that it supported the view that a third person’s DNA was in the sample, which would back up an assertion that Herskovic’s DNA was transferred to the sneaker by that third individual.

Tim Gough, the prosecutor on the case, repeatedly questioned Coyle’s qualifications, as he did when she was first offered as an expert witness. Coyle has not done any DNA testing since she left the Connecticut lab in 2004. Her graduate degrees are in plant biology. The sample in this case was 97.9 picograms.

“It’s still a relatively robust sample, correct?” Gough said of the sample.

“Yes,” Coyle said.

With his questions, Gough noted that evidence produced by high sensitivity DNA testing had been used in New York courts on “at least 20 different occasions” and that evidence produced by the Forensic Statistical Tool had been used by New York courts 43 times. Coyle, who co-authored a 2016 law journal article about the Forensic Statistical Tool, was unaware of those courts allowing that evidence in.

There are other public and private labs around the world that do high sensitivity DNA testing, but the medical examiner’s office appears to be the only lab that uses the method to develop evidence in criminal trials. Some European labs use it to develop leads in criminal investigations.

The technical leader of the medical examiner’s high sensitivity DNA testing lab was allowed to sit in court for Coyle’s testimony. He was joined by the criminalist who testified on August 30. They could be seen nodding in agreement and disagreement during her testimony. In some instances, they flashed broad grins when they apparently felt she said something that was incorrect.

The non-jury case is being heard by Judge Danny Chun. Juries can sometimes be too impressed by technical testimony or too suspicious of it. It is unlikely that Chun, who has been on the bench since 1999, will fall into either trap. Chun is a former prosecutor from Manhattan.

The defense rested on September19. The trial resumes on September 21, and the DNA lab technical leader will be called as a prosecution rebuttal witness. Closing statements are expected that day as well.